Field of the Invention
The present invention relates to mobile communication.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 10)”, 3GPP LTE/LTE-A may divide the physical channel into a downlink channel, i.e., a physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH), and an uplink channel, i.e., a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH).
In a wireless communication system, an uplink channel or a downlink channel needs to be estimated for transmission/reception of data, system synchronization acquisition, channel information feedback, and the like. In a wireless communication system environment, fading occurs due to a multi-path time delay. A process of restoring a transmission signal by compensating distortion of a signal, which occurs by a rapid environmental change due to the fading is referred to channel estimation. Further, a channel state for a cell to which a terminal belongs or another cell needs to be measured. For the channel estimation or measuring the channel state, the channel estimation is generally performed by using a reference signal (RS) which a transmitter and a receiver mutually know.
An uplink reference signal may be divided into a demodulation reference signal (DMRS) and a sounding reference signal (SRS). The DMRS is a reference signal used in the channel estimation for demodulating a received signal. The DMRS may be associated with transmission of a PUSCH or PUCCH. The SRS is a reference signal which the terminal transmits to a base station for uplink scheduling. The base station estimates an uplink channel through the received SRS and uses the estimated uplink channel in the uplink scheduling. The SRS may be periodically transmitted or when the base station needs to transmit the SRS, the SRS is triggered by the base station to be aperiodically transmitted.
Meanwhile, in a system in the related art, the sounding reference signal is not generally transmitted on a transmission region (alternatively, a resource region for the PUCCH) for the PUCCH.
However, a situation may be considered, in which the PUCCH is transmitted in a secondary cell (SCell) for the purpose of offloading for the PUCCH even with respect to a cell or a cell group having the same geographical position in a next system.
Accordingly, a transmission method of the sounding reference signal through a PUCCH region may be required for more efficient uplink scheduling.